Akt directly regulates focal adhesion kinase through association and serine phosphorylation: implication for pressure-induced colon cancer metastasis

Am J Physiol Cell Physiol. 2011 Mar;300(3):C657-70. doi: 10.1152/ajpcell.00377.2010. Epub 2011 Jan 5.

Abstract

Although focal adhesion kinase (FAK) is typically considered upstream of Akt, extracellular pressure stimulates cancer cell adhesion via Akt-dependent FAK activation. How Akt regulates FAK is unknown. We studied Akt-FAK interaction in colon cancer cells under 15 mmHg increased extracellular pressure. Pressure enhanced Akt-FAK association, blocked by inhibiting FAK or silencing Akt1 but not Akt2, and stimulated FAK serine phosphorylation in Caco-2 and human colon cancer cells from surgical specimens Akt1-dependently. FAK includes three serine (S517/601/695) and one threonine (T600)-containing consensus sequences for Akt phosphorylation. Studying S->A nonphosphorylatable point mutants suggests that these sites coordinately upregulate FAK Y397 tyrosine phosphorylation, which conventionally initiates FAK activation, and mediate pressure-induced cancer cell adhesion. FAK(T600A) mutation did not prevent pressure-induced FAK(Y397) phosphorylation or adhesion. Akt1 appeared to directly bind FAK, and this binding did not depend on the FAK autophosphorylation site (Y397). In addition, our results demonstrated that Akt phosphorylated FAK at three novel serine phosphorylation sites, which were also not required for FAK-Akt binding. This novel interaction suggests that FAK and Akt may be dual kinase targets to prevent cancer cell adhesion and metastasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenocarcinoma / etiology
  • Adenocarcinoma / metabolism*
  • Adenocarcinoma / pathology
  • Amino Acid Sequence
  • Caco-2 Cells
  • Catalytic Domain / genetics
  • Colonic Neoplasms / etiology
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / pathology
  • Focal Adhesion Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Focal Adhesion Protein-Tyrosine Kinases / metabolism*
  • Focal Adhesion Protein-Tyrosine Kinases / physiology
  • Gene Silencing / physiology
  • Humans
  • Neoplasm Metastasis / genetics
  • Neoplasm Metastasis / pathology*
  • Neoplasm Metastasis / prevention & control
  • Phosphorylation / genetics
  • Pressure / adverse effects*
  • Protein Binding / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-akt / physiology*
  • Serine / genetics
  • Serine / metabolism*

Substances

  • Serine
  • Focal Adhesion Protein-Tyrosine Kinases
  • Proto-Oncogene Proteins c-akt